Slaughter and May and Freshfields Bruckhaus Deringer are among four firms to have taken roles on the demerger of Reckitt Benckiser's pharmaceutical business.

Slaughters corporate partners Rebecca Cousin and Jeff Twentyman are leading for Reckitt and Indivior, the company's addiction control-focused pharma division, which will be demerged from the FTSE 100 group once shareholder approval is granted in December.

The Financial Times reported the new company is likely to be valued at between £2bn and £2.5bn.

Indivior, which will be UK-domiciled, is set to be admitted to the London Stock Exchange's main market for listed securities. Cousin and Twentyman are also leading on the listing, which is technically not an initial public offering as it does not involve a share offer.

In its announcement, Reckitt confirmed BP's general counsel Rupert Bondy will sit on Indivior's board as an independent director.

Freshfields is understood to be advising the sponsor banks and financial advisers, fielding a team led by capital markets and corporate partner Mark Austin, though the firm declined to comment on the deal.

Covington & Burling is advising Indivior's board, fielding a team led by New York-based M&A head Scott Smith, London corporate partner Simon Amies and US-qualified partner Peter Laveran, who recently returned to New York after more than a decade in the firm's London office.

Slaughters best friend firm Paul Weiss Rifkind Wharton & Garrison also advised Reckitt and Indivior on US-law matters, with London-based capital markets and securities head Mark Bergman leading a team alongside counsel Patricia Vaz de Almeida.

Last year Slaughters and Paul Weiss advised Reckitt on the issue by treasury subsidiary on two $500m bond issues.